Isocyanates, addition rearrangement

An acyl azide can rearrange donation ofthe nitrogen lone pair, 1,2-alkyl shift and loss of nitrogen gas occurs to give a highly reactive isocyanate, addition of benzyl alcohol to the carbonyl then occurs. 

The intermediates in making amines are isocyanates (0==C==N) just like the Hofmann Rearrangement. The isocyanates are decomposed with water, just like the Hofmann. In fact, there is a lot of similarity between the Hofmann and the Schmidt reactions. Before I detail the synthesis steps, I should note that if you wish to generate the Hydrazoic Acid in the flask by adding Sodium Azide, you might need a powder addition funnel. This bit of equipment is quite pricey and it s likely you won t have one, so the first part of the synthesis details how to make the Hydrazoic Acid separately. 

The third approaeh to synthetic polymers is of somewhat less commereial importance. There is in fact no universally accepted deseription for the route but the terms rearrangement polymerisation and polyaddition are commonly used. In many respects this process is intermediate between addition and condensation polymerisations. As with the former teehnique there is no moleeule split out but the kinetics are akin to the latter. A typical example is the preparation of polyurethanes by interaction of diols (di-alcohols, glycols) with di-isocyanates Figure 2.7). 

Fusion of an all cyclic ring onto the piperidine so as to form a perhydroisoquinoline is apparently consistent with analgesic activity. Synthesis of this agent, ciprefadol (68), starts with the Michael addition of the anion from cyclohexanone 56 onto acrylonitrile (57). Saponification of the nitrile to the corresponding acid ( ) followed by Curtius rearrangement leads to isocyanate Acid... 

The isocyanate formed on rearrangement adds water in a nucleophilic addition step to yield a carbamic acid. 

Additionally, uracil 6-iminophosphorane, isocyanate, and o-methyl-e-caprolactim ether join to form the intensely yellow pyrimido[4 5 4,5] pyrimido[6,l-n]azepine (360), as shown in Scheme 130. Upon ring closure, methanol is spontaneously eliminated. Diethyl azodicarboxylate affords with the other components pyrimido[4,5-e][l,2,4]triazoline (361), which is closely related to the alkaloid isofervenuline. The imidazo[5, -/][ ,2,4]tria-zine (362) results in a known Michael-type rearrangement sequence by treatment with diethyl acetylenedicarboxylate (86JOC149, 86JOC2787) in this latter case, the Michael-type addition occurs much faster than the expected three-component reaction [93H(35)1055]. 

Thioxo-1,2,4-dithiazolidines can be obtained from thioxo-l,2,4-thiadiazolidines by Dimroth rearrangement (Scheme 47) or reversibly by addition and elimination of acetone (Scheme 22). 1,2,4-Dithiazole type products are also obtained from thiocarbonyl isothiocyanates (154) by reaction with CI2 <84CHEC-I(6)897>, PhMgBr, Sj, or CS2. Other routes include reactions of carbonyl isothiocyanates and thiocarbonyl isocyanates with P4S10 or Sg <84Chec-I(6)897> and sulfonyl isocyanates with dialkyl thioketenes. Phenylisothiocyanate heated with N,C-disubstituted oxaziridines affords 3,5-diimino-l,2,4-dithiazolidines (226, 227). Other miscellaneous syntheses of 1,2,4-dithiazoline derivatives include cyclization of A7-thioacyl hexafluoroacetonimine to 5,5-bis(trifluoromethyl)-... 

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